1. Field of the Invention
This invention relates to a fuel control apparatus for an internal combustion engine and, more particularly, to a fuel control apparatus system for an internal combustion engine which employs an electronically controlled fuel injection device.
2. Description of the Prior Art
FIG. 1 shows a conventional fuel control apparatus for an internal combustion engine of a motor vehicle. An intake tube 1, which is connected to the intake port of the engine, defines a fuel and air mixing chamber 2. The mixing chamber 2 has a fuel control valve 3 for supplying fuel into the chamber 2 and a throttle valve 4, which is disposed downstream of the valve 3, for controlling the flow rate of a fuel-air mixture. The fuel control valve 3 is electrically connected to a control device 5. The control device 5 is also electrically connected to a sensor, which is provided in the intake tube 1 and located upstream of the fuel control valve 3, for detecting the quantity of the air coming into the intake tube (for example, an air sensor 6 of the hot wire type), and a water temperature sensor 8 is located on the body of the engine 7 for detecting the temperature of water in a cooling jacket. An air cleaner 9 is provided at the inlet of the intake tube 1.
According to the apparatus described above, an optimum quantity of fuel is calculated in the control device 5 in accordance with the quantity of incoming air and the engine temperature determined by the air sensor 6 and the water temperature sensor 8, respectively. A drive signal is then transmitted to the fuel control valve 3 in accordance with the results of the above calculation to control the flow rate of the fuel which is supplied through the valve 3. According to this conventional arrangement, however, the control device 5 is mounted in a vehicle compartment away from the engine since the control device utilizes electronic parts which cannot be heated above a predetermined temperature. Accordingly, it has been difficult to mount the control device in an engine compartment in which high temperatures prevail. The installation of the control device 5 in a vehicle compartment which is displaced from the intake passage 2, as well as from the engine, requires a great deal of wire. In addition, such an installation also requires a great deal of time and labor to complete the electrical wiring since the control device is spaced a considerable distance from the fuel control valve 3, the air sensor 6 in the mixing chamber 2, and the water temperature sensor 8 on the engine. The installation of the device 5 in a vehicle compartment which is spaced away from the engine is further disadvantageous in that the associated electrical wiring is sometimes influenced by noise which is transmitted from the wiring of other instruments in the vehicle.
If the control device 5 is spaced apart a long distance from the fuel control valve 3, the air sensor 6 and the water temperature sensor 8, it is difficult to make the necessary adjustments for improving the accuracy of the entire control system on the motor vehicle. Accordingly, the fuel control valve 3, the control device 5 and the air sensor 6 must be designed with a high degree of accuracy and are, therefore, expensive. The conventional apparatus also requires a large radiating member for cooling the circuits of the various sections of the control device 5 (for example, a switching element and a power source circuit for driving the fuel control valve 3), as they are likely to generate a great deal of heat.